1. Field of the Invention
The present invention generally relates to a vibration-damping device adapted to be mounted on a vibrative member so as to function as a secondary vibration system with respect to the vibrative member as a primary vibration system, for thereby damping vibrations excited in the vibrative member. More specifically, the present invention is concerned with such a vibration-damping device that is novel in construction and that is capable of exhibiting an excellent damping effect with respect to vibrations over a relatively wide frequency range.
2. Description of the Related Art
A dynamic damper is widely known as one type of vibration-damping devices for damping vibrations excited in a vibrative member, such as a body of an automotive vehicle. The known dynamic damper includes a mass and a spring system, and is mounted on the vibrative member for providing a secondary vibration system with respect to the vibrative member as a primary vibration system.
However, the known dynamic damper is not able to exhibit a desired damping effect with respect to vibrations over a wide frequency range, since a damping effect of the known dynamic damper is limited to a relatively narrow frequency range to which a natural frequency of the secondary vibration system is tuned.
Moreover, the known vibration-damping device causes undesirable increase of transmissibility at two frequency ranges located upper and lower sides of the frequency range to which the natural frequency of the secondary vibration system is tuned, inevitably suffering from deterioration of a vibration condition of the vibrative member.
This conventional problem experienced in the known dynamic damper, namely, undesirable increase of the transmissibility at the lower and higher frequency range of the tuning frequency of the secondary vibration system, may be eliminated or minimized by giving a sufficiently high damping effect to the spring system of the dynamic damper. In view of the above, it is proposed to make the spring system out of a rubber elastic body having a high damping capability. In this case, however, the damping characteristics of the spring system formed by the rubber elastic body is likely to be influenced by the ambient temperature. Therefore, the known dynamic damper may suffer from difficulty in exhibiting a desired damping effect with high stability due to a considerable change of the ambient temperature, depending upon a portion where the dynamic damper is installed.